The invention provides a lift blade and engagement shed-forming apparatus for a textile machine and, in particular, a loom.
One form of shed-forming device for a textile machine, comprises lift blades which are movable in opposite relationship to each other, and hooking engagement elements which can be engaged by the lift blades in a hooking engagement position, and which are connected in pairs by flexible connecting members forming loop configurations. The device further includes rollers carried in the loops, operatively connected to the shedding means, such as the heald train or harness train of the textile machine. Stationary electromagnetic means act on the hooking engagement elements holding the elements in position and are adapted to be actuated by way of program carriers.
In the preferred embodiment of the invention each of the pair of hooking engagement elements is capable of being positioned in either of two discrete vertical locations. Specifically, when one of the hooking engagement elements is in the engaged position, i.e., engaged by the lift blades and moved upwardly into the upper-shed position, the other of the pair of hooking engagement elements is held in a lower-shed position. In the preferred embodiment, one element is retained in the upper-shed position if a change in shed is to be effected by the harness connected to the roller.
Another device of the general kind outlined above is disclosed, in European patent specifications Nos. 0 188 074 and 0 119 787. In those devices the hooking engagement element must be attracted by the magnets across a respective air gap in order to be held in a desired position. Thus, the part of the hooking engagement element to be attracted by the magnet means is of a long and blade-like configuration. This air gap requires that the electromagnet device produce a strong attractive force, which, inter alia, gives rise to a relatively high level of power consumption. Furthermore, this arrangement produces a large amount of heat, and requires a large space to accomodate an appropriate electromagnet.
The shed-forming device disclosed in European patent specification No. 0 219 437, operates with a weak electromagnet means; however, that configuration does not involve any air gap which has to be traversed. To provide such a design configuration, the arrangement requires additional arresting elements; e.g., pivotal levers which are additionally supported with hooks and springs. Accordingly, the additional mounting means subject the levers to heavy loadings and, in general, the additional components result in greater expense and increased incidences of malfunction.